There is a major need for a pyrotechnic piston device, such as a piston actuator, that will have a very long shelf life, that will not be plagued by the problem of blow-by, that maintains the piston in the full-forward position after firing, that is highly effective and reliable, and that is relatively simple and economical to manufacture.
Referring, for example, to shelf life, this is of great importance in many fields, but especially to the military. It is intolerable if the effectiveness of a seal between the piston and the cylinder degrades with time. Such degrading coul cause a malfunction of a crucial component in a missile, for example. Thus, O-rings and other rubber or synthetic resin seal elements are unsatisfactory and often totally unacceptable.
When a seal between the piston and the cylinder degrades, there is blow-by of gaseous and other products of the explosion. Such products pass by the piston, emanate from the cylinder, and may cause severely adverse effects. Furthermore, the blow-by reduces the amount of force that is exerted on the piston.
Even when an O-ring, or other seal formed of rubber or synthetic resin, is new and not at all degraded, there may be blow-by because of the heat and pressure effects that the pyrotechnics exert on (for example) an O-ring.
Referring next to one of the major factors other than shelf life and blow-by, it is essential in piston actuators that the load against which the piston works not cause the piston to bounce back into the cylinder, either wholly or partially. Thus, effective means must be provided to prevent such rebound.
In addition to the above-mentioned factors, there are the ever-present problems of production cost, reliability, effectiveness, simplicity, etc. A truly excellent pyrotechnic piston device must satisfy all of these requirements besides overcoming the problems of shelf life, blow-by and rebound.